Aluminum alloy

ABSTRACT

AN ALUMINUM BASE ALLOY CAPABLE OF RECEIVING AN ALKALINE ETCH TREATMENT TO PRODUCE A UNIFORM MAT FINISH CONTAINS SILICON IN AN AMOUNT IN THE RNGE 0.2-0.6%, IRON IN THE AMOUNT 0.35% MAX., MANGENESE IN THE AMOUNT 0.10% MAX., MAGNESIUM IN AN AMOUNT IN THE RANGE 0.45-0.9%, CHROMIUM IN THE AMOUNT 0.1% MAX., TITANIUM IN THE AMOUNT 0.10% MAX., ZINC IN THE AMOUNT IN THE RANGE 0.03-0.25% AND COPPER IN AN AMOUNT IN THE WEIGHT RATIO 1:1 TO 2:1 ON A CU-ZN WEIGHT BASIS RATIO, OTHERS EACH IN THE AMOUNT 0.05% MAX., SAID OTHERS TOTAL IN THE AMOUNT 0.15% MAX., THE REMAINDER BEING ALUMINUM, ALL THE AFORESAID PERCENTAGES BEING PERCENT BY WEIGHT. OF THE ABOVE-MENTIONED ALLOYS WHEN THE ZINC CONTENT IS IN THE RANGE 0.10-0.25% THE COPPER SHOULD BE PRESENT IN AN AMOUNT IN THE WEIGHT RATIO 2:1 ON A CU-ZN WEIGHT BASIS RATIO AND, ALSO, IN THE ABOVE ALLOYS WHEN ZINC IS PRESENT IN AN AMOUNT IN THE RANGE 0.03-0-10% THE COPPER SHOULD BE PRESENT IN AN AMOUNT IN THE WEIGHT RATIO 1:1 ON A CU-ZN WEIGHT BASIS RATIO.

United States Patent Int. Cl. C23f 1/00 US. Cl. 29-183 3 Claims ABSTRACT OF THE DISCLOSURE An aluminum base alloy capable of receiving an a1ka line etch treatment to produce a uniform mat finish contains silicon in an amount in the range 0.2-0.6%, iron in the amount 0.35% max., manganese in the amount 0.10% max., magnesium in an amount in the range 0.450.9%, chromium in the amount 0.1% max., titanium in the amount 0.10% max., zinc in the amount in the range 0.030.25% and copper in an amount in the weight ratio 1:1 to 2:1 on a Cu-Zn weight basis ratio, others each in the amount 0.05% max., said others total in the amount 0.15% max., the remainder being aluminum, all the aforesaid percentages being percent by weight. Of the above-mentioned alloys when the zinc content is in the range 0.100.25% the copper should be present in an amount in the weight ratio 2:1 on a Cu-Zn weight basis ratio and, also, in the above alloys when zinc is present in an amount in the range 0.030.10% the copper should be present in an amount in the Weight ratio 1:1 on a Cu-Zn weight basis ratio.

This invention relates to aluminum alloys. More particularly, this invention relates to aluminum alloys capable of being extruded in a wide variety of forms or shapes and having utility in the architectural and other fields. More particularly this invention relates to aluminum alloys of the type known as AA6063.

Aluminum alloys of the type No. 6063 have the com position in percents by Weight Si 0.20-0.6, Fe 0.35 max., Mn 0.10 max., Mg 0.45;0.9, Cr 0.10 max., Ti 0.10 max., Zn 0.10 max., Cu 0.10 max., others, each 0.05 max. and said others, total 0.15 max., the remainder being aluminum. These alloys prior to use, particularly prior to anodizing, receive an alkaline etch treatment, such as by contact with a sodium hydroxide containing solution, so as to produce thereon an attractive finish.

It has been established that in the etching of aluminum alloys an undesirable etched surface appearance, i.e. a grainy or spangle appearance results from the grains of the alloy structure being attacked at the different rates during etching. This is due to the presence of excessive zinc in the alloy. Generally, zinc in these alloys is present as an impurity and comes from either the bauxite from which the aluminum constituent of the alloy is derived and/or from the scrap material used in the preparation of the alloy.

It has been observed that when alloys of the type No. 6063 containing zinc in an amount in excess of 0.03%, such as 0.05%, are etched in a solution of sodium hydroxide, these alloys tend to yield a grainy surface appearance. Since it is difficult to consistently produce on a commercial scale type No. 6063 alloys having a zinc content below about 0.03%, the development of a method of etching type No. 6063 alloys having a zinc content greater than 0.03% to yield a uniform mat finish would be useful and of major commercial importance.

Accordingly, it is an object of this invention to provide a type No. 6063 aluminum alloy having a zinc content greater than 0.03% and capable when subjected to 3,594,133 Patented July 20, 1971 an alkaline etch treatment of yielding a uniform etch finish, such as a uniform mat finish.

It is another object of this invention to provide an aluminum alloy of the type No. 6063 and containing zinc in an amount in the range 0.030.25% and capable, when subjected to an alkaline etch treatment, of yielding a uniform etch finish, such as a uniform mat finish.

How these and other objects of this invention are attained will become apaprent in the light of the accompanying disclosure.

It has been discovered that zinc-containing aluminum alloys, particularly aluminum alloys of the type No. 6063 having a zinc content greater than 0.03% by weight, can be etched to produce a uniform etch finish, such as a uniform mat finish, provided there is present in the zinc-containing aluminum alloy an amount of copper in the weight ratio 1:1 to 2:1 on a Cu-Zn weight basis ratio. Specifically, and in accordance with one embodiment of this invention, when the zinc content of such alloys is present in an amount in the range 0.030.10% copper should be present in the alloy in the Weight ratio 1:1 on a Cu-Zn Weight basis ratio so that when the alloy is subjected to an alkaline etch treatment, such as by contact with a sodium hydroxide-containing solution or its equivalent, the resulting etched alloy receives a uniform mat finish. In accordance with yet another embodiment of the practice of this invention, when such zinc-containing aluminum alloys contain an amount of zinc in the range 0.10-0.25%, copper should be present in an amount in the weight ratio 2:1 on a Cu-Zn weight basis ratio so that when such alloys are subjected to an alkaline etch treatment the resulting etched alloy receives a uniform mat finish.

Accordingly, in accordance with this invention, when an aluminum alloy of the type No. 6063 contains a zinc content in the range 0.030.10% there should also be included copper in an amount substantially the same as or the same as the zinc content on a Cu-Zn weight basis ratio of 1:1. Specifically, when the zinc content of such alloys is 0.05% by Weight, the copper content of such alloys should be 0.05% by weight also so that such alloy can be subjected to an alkaline etch treatment to yield a uniform mat finish. Likewise, when the zinc content of such alloys is in the amount 0.10% by weight, the copper content of such alloy should be 0.10%. When, however, the zinc content of such alloys is greater than 0.10% by Weight, such as an amount in the range 0.120.25% by weight, the amount of copper in such alloys should :be twice the zinc content such that the weight basis ratio CuzZn is 2:1. Specifically, in accordance with this embodiment of the invention when the zinc content of these alloys is 0.15% by weight the copper content of such alloy should be 0.30% by weight so that when the alloy is subjected to an alkaline etch treatment the resulting etched alloy receives a uni-form mat finish. Likewise, when the zinc content of such alloys is 0.25% by Weight, the copper content of the alloys should be 0.50% by weight so that the alloy when subjected to an alkaline etch treatment will receive a uniform mat finish.

The following examples are illustrative of the practice of this invention:

EXAMPLE 1 When an aluminum alloy having the composition in the following percents by weight, Fe 0.17, Mg 0.51, Mn 0.1, Si 0.46, Ti 0.01, Zn 0.088 and Cu 0.01, the remainder being aluminum, was etched with a standard etching solution (50 g./l. Diversey Aluminux, a proprietary caustic etchant solution, plus 0.2 g./l. of dissolved alluminum) at 65 C. for 2, 5 and 10 minutes,

the resulting etched aluminum alloy showed a pronounced grainy appearance indicating a pronounced preferential grain type of attack during etching. In this alloy tested the copper content was much less than the zinc content with the result that a satisfactory etch finish was not obtained.

EXAMPLE 2 Aluminum alloys of type No. 6063 containing various level combinations of zinc and copper content were etched in a solution of 50 g./l. of Diversey Al'uminux plus 0.2 g./l. of dissolved aluminum at 65 C. for 10 minutes. The effects of zinc and copper content in the alloys upon the etched fiinsh are indicated in the accompanying table:

P.G.A.=preferential grain attack. P.G.B.A.=preferential grain boundary attack.

The results reported in above Table I indicated that when the zinc content is less than 0.03% a uniform etch appearance is obtainable. When, however, the zinc con tent is greater than 0.03% by weight a uniform etch appearance is not obtainable save the instance where copper is present in said alloys in an amount equal to or at least equal to the zinc content. The tests further show that when the zinc content is 0.10% a grainy etched appearance is obtained if the copper content of the alloy is much less than the zinc content but when the copper content is equal to the zinc content there is produced a uniform etched appearance. The above test results show that the etfect of zinc is minimized by including copper in the alloy on a substantially 1:1 Weight basis ratio with respect to the zinc.

EXAMPLE 3 Additional tests were carried out on extruded aluminum alloys of type No. 6063 and it was found that for such alloys having a zinc content up to 0.10% by Weight the presence of copper in the alloy in an amount equal to the zinc, i.e. on a 1:1 Weight basis ratio, there were produced acceptable etched surface finishes free of grainy ap pearance. With respect to artificially aged (T5 temper) similar etched alloys the same affect was also noticed with a zinc content of 0.05%. However, with a zinc content greater than 0.10% an increase in addition of copper amounting to twice the zinc content, i.e. on the 2:1 weight basis ratio of CuzZn, is called for so that a satisfactory etch finish is obtained.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many modifications,

4 alterations and substitutions are possible in the practice of this invention without departing from the spirit or scope thereof.

We claim:

1. An etched article consisting essentially of silicon in an amount in the range 0.200.6%, iron in the amount 0.35% max., manganese in the amount 0.10% max., magnesium in an amount in the range 0.450.9%, chro rnium in the amount 0.1% max., titanium in the amount 0.10% max., zinc in an amount in the range 0.030.10% and copper in the amount at the weight ratio 1:1 on a CuzZn weight basis ratio, others or impurities each in the amount 0.05% max., the total of said others or impurities being in the amount 0.15% max., the remainder being aluminum, all the aforesaid percentages being percents by Weight, and characterized by a uniform mat finish produced by perferential grain boundary attack, said etched article having been subjected to an alkaline etch treatment.

2. An etched article consisting essentially of silicon in an amount in the range 0.20-0.6%, iron in the amount 0.35% max., manganese inthe amount 0.10% max., magnesium in an amount in the range OAS-0.9%, chromium in the amount 0.1% max., titanium in the amount 0.10% max., zinc in an amount in the range 0.10-0.25% and copper in an amount at the weight ratio 2:1 on a CuzZn weight basis ratio, others or impurities each in the amount 0.05 max., the total of said others or impurities being in the amount 0.15% max., the remainder being aluminum, all the aforesaid percentages being percents by weight, and characterized by a uniform mat finish produced by preferential grain boundary attack, and etched article having been subjected to an alkaline etch treatment.

3. An etched article consisting essentially of silicon in an amount in the range 0.200.6%, iron in the amount 0.35% max., manganese in the amount 0.10 max., magnesium in an amount in the range OAS-0.9% chromium in the amount 0.1% max., titanium in the amount 0.10% max., zinc in an amount in the range 0.03-0.25 others or impurities each in the amount 0.05% max., the total of said others or impurities being in the amount 0.15% max., copper being present in an amount at the weight ratio 1:1 on a CuzZn weight basis ratio when zinc is present in an amount in the range 0.03-0.10% and copper being present in an amount at the weight ratio 2:1 on a CuzZn weight basis ratio when zinc is present in an amount in the range 0.10-0.25%, the remainder being aluminum, all the aforesaid percentages being percents by weight, and characterized by a uniform mat finish produced by preferential grain boundary attack, said etched article having been subjected to an alkaline etch treatment.

References Cited UNITED STATES PATENTS 3,104,189 9/1963 Wagner 141 RICHARD O. DEAN, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 1.59 8 33 Dated July 20, 1971 Patent No.

Spooner Inventor(s) Jacques F. Cote, William Ernest Cooke and Roy C.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line +2, "O.H5;O.9, should read 0. +5-O.9

line 63, the word "etched" should appear after "grainy" Column 3, Table I, under the heading "Predominant type of attack" the phrase "Light P.G.B.Ag" should read Light P.G.B.A.

Column t, Claim 2, line 13, "and" should read said Claim 3, line 3, "0.10 max., should read 0.10% max.,

Signed and sealed this 15th day of February 1972.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER, JR.

Commisioner of Patents Attesting Officer FORM E D-1 01 1 USCOMM-DC 6O37fi-D614 U 5. GOVERNMENT FRFNTING OFFICE I959 ()366'J34 

